1. Field of the Invention
The present invention pertains to a child-resistant, safety closure for packaging ingredients such as household chemicals, medicaments, or other ingredients, which may be dangerous and harmful to children and other persons of insufficient mental capacity to appropriately comprehend the threat of serious injury or death posed by contact with, or improper use of, such ingredients. Thus, the closure is of the type which is constructed in such manner that its removal from the container requires that a knowledgeable and purposeful thought process be employed in conjunction with a manual dexterity which is beyond the capabilties of an immature child or a person of similar mental faculties.
2. Description of the Prior Art
Heretofore, numerous versions of safety closures have been designed for the purpose of preventing children and other unknowledgeable persons from gaining access to dangerous household chemicals, medicaments and drugs such as are conventionally packaged in containers for consumer use. Among such types of safety closures are those which are of the non-reusable type associated with unit dose or single use containers. However, many types of dangerous and harmful household chemicals, medicines, and the like, characteristically are of the type which are packaged for frequent, repeated usage, or dispensation, and thereby require the employment of a safety closure which is susceptible to being frequently removed and reattached on the container, while at the same time retaining the features of being a child-resistant, safety closure. Among the latter types of safety closures which have attained substantial commercial acceptance are those which are frequently referred to as "squeeze-and-turn" types of safety closures. Various prior art types of patented squeeze-and-turn safety closures are described in, among others, U.S. Pat. Nos. 3,984,021 and 3,376,991 which require major modifications in the shape of the container neck portion in order to accommodate adequate deformation of the safety closure in response to manual compression, or squeezing to disengage it from the container.
Another version of a squeeze-and-turn safety closure designed for use with a container having a more conventionally styled circular neck portion is described in U.S. Pat. No. 3,941,268. While the last-mentioned patent provides a safety closure construction which features such advantages as being utilizable with a container having a more conventional type of neck portion and which also provides a highy desirable secondary interlock between the safety closure and the container neck portion, the seal between the closure and container may be impaired during use and permit leakage of the container's contents.
A serious problem existent with most of the known safety closures resides in the common use of a sealing liner positioned on the underside surface of the closure, and which is arranged to abut and seal against the annular rim on the container neck portion to prevent leakage of the container's contents. Customarily, most of the commonly employed sealing liners are fabricated in the form of thin discs of resilient plastic material which is sufficiently pliant to accommodate small imperfections in the rim surface of the container neck portion and provide a fluid-tight seal therewith. However, it is not uncommon for such plastic sealing materials to undergo plastic flow when compressed repetitively, or for prolonged periods of time, against the annular rim on the neck portion of the container. As a result, during the course of repeated removal and replacement of the closure in order to reach a fully closed position, the closure frequently must be further and further tightened to compensate for such liner deformation. As a result, the fully closed and sealed position of the closure gradually changes and causes a corresponding change in the rotational position of the closure relative to the container neck portion. However, since the relative rotational orientation of the interlocking members provided on the container and the safety closure remains unchanged, the fully closed and sealed position of the closure no longer orientationally corresponds to the original interlocking, fully closed position. Thus, leakage of the container's contents is apt to occur in the event that the safety closure is loosened or otherwise returned to its original fully closed and interlocked location on the neck portion of the container. Consequently, although the safety closure may be positioned in its original fully closed position in interlocked engagement with the container, the sealing liner may have been rendered ineffective to prevent leakage of the container's contents. Thus, a child while handling the container may come into harmful or injurious contact with the contents leaking from the container.
Also, many of the patented prior art types of squeeze-and-turn safety closures employ readily observable, exposed tabs and complementary detents on the closure and container for purposes of preventing closure removal. Indicative of patents employing such exposed tabs are previously mentioned in U.S. Pat. No. 3,984,021 and such other representative patents as U.S. Pat. Nos. 3,770,153; 3,826,395; 3,830,391 and 3,841,514. Among other possibilities, the repeated flexing or stressing of such tabs renders them susceptible to being weakened in consequence of stress damage, and thus apt to failure when subjected to even minimal force such as might be exerted by a child attempting to remove the closure. No less importantly, the exposed and observable presence of such tabs makes them more susceptible to being disengaged from the container by an inquisitive child.